The present disclosure relates to networked communications, and particularly to a presence service adapted for use with mobile devices.
Many individuals can now be contacted through several of a variety of services, such as a land-line telephone connection, a mobile telephone connection, a push-to-talk (PTT) voice connection, one or more instant messaging accounts, and one or more electronic mail accounts. Given these choices, it can be difficult to determine how an individual can best be contacted at a given time, if he can even be contacted at all. To address this issue, various “presence” services have become available. Presence services allow an individual and/or the devices he uses for communications to share information on the state of the individual and/or those devices. The entity providing presence information is commonly referred to as a “presentity.” Those entities that learn about the presence state of a presentity are commonly referred to as “watchers.” Watchers wishing to contact the individual can, if they are authorized, learn the presence state of the presentity to determine how, if at all, the presentity should be contacted.
Certain existing or proposed presence systems are outlined in various “Internet Request for Comments” (RFC) documents, generally available at <http://tools.ietf.org/rfc/> and indexed by RFC number. Such RFCs include RFC 2778, “A Model for Presence and Instant Messaging”; RFC 2779, “Instant Messaging/Presence Protocol Requirements”; RFC 3856, “A Presence Event Package for the Session Initiation Protocol (SIP)”; RFC 3863, “Presence Information Data Format (PIDF)”; RFC 3921, “Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence”; and RFC 3859, “Common Profile for Presence (CPP).”
Other existing or proposed presence systems have been outlined in specifications prepared by the Open Mobile Alliance, available generally at <http://www.openmobilealliance.org/release_program/index.html>.
One challenge faced by presence systems is to balance two competing needs. On the one hand, it is desirable for presence information to be kept as up-to-date as possible. On the other hand, particularly where wireless mobile stations are involved, the amount of messaging needed to share up-to-date presence information can put noticeable strains on bandwidth, computational resources, and battery power. This challenge has been addressed in various ways. As one example, J. Brock, in “Regulating Publication of Event State Information” (Mar. 6, 2006) available at <http://tools.ietf.org/html/draft-brok-simple-regulate-publish-02>, proposes various solutions to the problem that “[o]n a mobile device, monitoring resources in order to publish changes of the presence state can be costly in terms of battery and computing resources. Even worse, publishing information regularly over a cellular network can have a dramatic effect on the battery lifetime, number of messages and transmitted data volume.” Taking another approach, T. Moran et al., in “Requirements for Presence Specific Event Notification Filtering” (Jan. 26, 2004), available at <http://tools.ietf.org/html/draft-ietf-simple-pres-filter-reqs-03>, propose a filtering mechanism to reduce the number of presence-related messages received by a wireless device.